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The efficiency of a screw jack is maximum, when (where α = Helix angle, and φ = Angle of friction)
α = 45° + φ/2
α = 45° - φ/2
α = 90° + φ
α = 90° - φ
α = 45° + φ/2
α = 45° - φ/2
α = 90° + φ
α = 90° - φ